1. Field of the Invention
The present subject matter relates generally to a multi-layer structure in a reaction cell for growing a diamond and a method of providing the multi-layer structure, particularly to a multi-layer structure including a multi-layer metal solvent catalyst for stabilizing the initial diamond crystal growth by the temperature gradient method and a method of providing the same.
2. Related Art
Growing diamond crystals using a high temperature and high pressure processes via a temperature gradient method is generally known in the art, for example, as described in U.S. Pat. No. 4,034,066. As a result of subsequent large-scale production, grown diamonds are commercially available as heat sinks, super-precision cutting tools, and other fabricated products.
The diamond growth process includes a reaction cell which contains graphite as a carbon source, a diamond seed crystal, and a solvent metal. The solvent metal separates the carbon source from the seed crystal. During growth of diamond crystals, the carbon source dissolves into the solvent metal upon heating, and a temperature gradient exists between the carbon source and seed crystal. Temperature and pressure are regulated to permit diamond crystal growth on the seed crystal. By very carefully adjusting pressure and temperature and utilizing a small temperature gradient with extended growth times, larger diamonds can be produced. However, attempts to increase crystal sizes have shown a strong tendency for spontaneous nucleation of diamond crystals to occur at the underside of the molten catalyst-solvent metal. This develops into a serious problem, because the diamond nucleation occurring near the seed diamond competes with the growth from the seed diamond, resulting in the development of multiple crystals which collide as they grow. In addition, the seed diamond may be dissolved if the metal solvent composition is improper, resulting in no growth from the seed crystal at all.
The prior art for the growth of diamonds uses a single layer metal catalyst that provides a fixed composition of the solvent catalyst. A disadvantage of only a single layer metal catalyst is that high quality single diamond crystal growth can only be achieved by a precise control of temperature and/or pressure. If the temperature is too high, the seed diamond will be completely dissolved and thereby no diamond growth will be obtained. On the other hand, if the temperature is too low, the tendency of spontaneous nucleation will be increased. To increase the productivity, the temperature gradient is preferably set as high as possible. This will, however, increase the tendency of spontaneous nucleation. Thus, according to the prior art adopting a single-layer metal catalyst, the operable pressure/temperature window for high-quality diamond crystals is narrow. For commercial High Pressure High Temperature (HPHT) diamond production, it is preferable to have a wider operating window for high quality diamond crystal growth.